Bug 1677334 - Part 1: Don't generate click event for mouse-left-down with ctrl key is pressed on Mac; r=masayuki

Chrome and Safari doesn't genereate click event when contorl key is pressed, either.

Differential Revision: https://phabricator.services.mozilla.com/D109903

gfx/layers/apz/src/APZInputBridge.cpp

@@ -142,9 +142,19 @@ APZEventResult APZInputBridge::ReceiveInputEvent(WidgetInputEvent& aEvent) {
         mouseEvent.mRefPoint.y = input.mOrigin.y;
         mouseEvent.mFlags.mHandledByAPZ = input.mHandledByAPZ;
         mouseEvent.mFocusSequenceNumber = input.mFocusSequenceNumber;
+#ifdef XP_MACOSX
+        // It's not assumed that the click event has already been prevented,
+        // except mousedown event with ctrl key is pressed where we prevent
+        // click event from widget on Mac platform.
+        MOZ_ASSERT_IF(!mouseEvent.IsControl() ||
+                          mouseEvent.mMessage != eMouseDown ||
+                          mouseEvent.mButton != MouseButton::ePrimary,
+                      !mouseEvent.mClickEventPrevented);
+#else
         MOZ_ASSERT(
             !mouseEvent.mClickEventPrevented,
             "It's not assumed that the click event has already been prevented");
+#endif
         mouseEvent.mClickEventPrevented |= input.mPreventClickEvent;
         MOZ_ASSERT_IF(mouseEvent.mClickEventPrevented,
                       mouseEvent.mMessage == eMouseDown ||

widget/cocoa/nsChildView.mm

@@ -2970,10 +2970,12 @@ NSEvent* gLastDragMouseDownEvent = nil;  // [strong]
   geckoEvent.mClickCount = clickCount;
 
   if (!StaticPrefs::dom_event_treat_ctrl_click_as_right_click_disabled() &&
-      ([theEvent modifierFlags] & NSEventModifierFlagControl)) {
+      geckoEvent.IsControl()) {
     geckoEvent.mButton = MouseButton::eSecondary;
   } else {
     geckoEvent.mButton = MouseButton::ePrimary;
+    // Don't send a click if ctrl key is pressed.
+    geckoEvent.mClickEventPrevented = geckoEvent.IsControl();
   }
 
   mGeckoChild->DispatchInputEvent(&geckoEvent);

widget/tests/test_mouse_event_with_control_on_mac.html

@@ -63,6 +63,11 @@ function waitAndCheckMouseEvents(aTarget, aExpectedEvents) {
 
 add_task(async function Init() {
   await SimpleTest.promiseFocus();
+
+  let target = document.getElementById("target");
+  target.addEventListener("click", function() {
+    ok(false, `should not receive click event`);
+  });
 });
 
 add_task(async function TestMouseClickWithControl() {
@@ -73,8 +78,7 @@ add_task(async function TestMouseClickWithControl() {
   let target = document.getElementById("target");
   let promise = waitAndCheckMouseEvents(target, [["mousedown", 0, true],
                                                  ["contextmenu", 0, true],
-                                                 ["mouseup", 0, true],
-                                                 ["click", 0, true]]);
+                                                 ["mouseup", 0, true]]);
   synthesizeNativeMouseEvent({
     type: "click",
     target,